Many varied types of lighting devices are available to provide lighting for many different functions. Different lighting functions require, or benefit from, light of particular characteristics. The required, or beneficial, light characteristics are not necessarily static and the light characteristics sometimes need to be altered, such as to increase the intensity of the light or decrease its intensity.
Entertainment lighting, for instance, provides lighting for entertainment activities, such as stage lighting and the like. Entertainment lighting includes a wide array of light-generative devices that generate light energy of many varied characteristics. Light-generative elements are supported at, or form part of, lighting fixtures. Entertainment lighting includes, e.g., incandescent light sources as well as other types of discharge light sources, such as high intensity discharge (HID) or florescent lamps.
Various devices have been developed and are used to control the light output intensity of light generated by the entertainment lighting fixtures, as well as other types of lighting. Additional such devices provide for the balancing or adjusting of light output of multiple lighting fixtures facilitate desired lighting effects at a stage setting, a studio setting, a building, room, or any other location that is to be lighted.
One general manner by which to control the light output of the lighting fixtures is by controlling the electrical signal that feeds the light source. That is to say, the light output of the light fixture is altered by altering the power levels of power provided to power the light source of the lighting fixture. For instance, the light output of an incandescent lamp is controlled by raising and lowering the voltage applied to the lamp, controlling the current applied to the lamp, or by adjusting the wave form of the power that is applied to the lamp. Various of such devices are regularly used. This manner of controlling the light intensity of the light output suffers from the disadvantage that the color temperature and color spectrum of the light output as well as adjusting the output. As an incandescent lamp is dimmed, the light output becomes shifted towards the red frequencies of the light spectrum.
High intensity discharge lamps are also sometimes dimmed by analogous mechanisms. However, high intensity discharge lamps also suffer from an analogous disadvantageous color shifting that occurs with incandescent lamps with the dimming of the lamp output causing shifting of the light output toward the blue frequencies of the light spectrum. Additionally, the extent of the dimming is limited. That is to say, the range of the permitted dimming is limited. For instance, a high intensity discharge lamp is able to be dimmed down to 25-50% of its full output. But, unlike an incandescent lamp, the dimming cannot continue down to a zero output.
High intensity discharge lamps suffer from the further disadvantage of long lag times to re-illuminate, once the lamp output is extinguished. That is to say, once extinguished, a high intensity discharge lamp requires a significant amount of time to re-illuminate and return to a normal operating light output. This delay, for some lighting functions, particularly entertainment lighting functions, is unacceptably lengthy. A theatrical lighting fixture, for instance, must be able to illuminate precisely on cue, and with no acceptable delay.
Mechanical dimming devices are sometimes used to dim a light source. The disclosures of U.S. Pat. Nos. 1,146,143; 2,735,929; 3,433,142; 4,257,086; and 6,102,554 are all exemplary of mechanical devices available to dim light output. These exemplary disclosures, in general, provide for the fitting of a light source with a multi-leaf iris element. Arrangement of the iris element controls the light output. Use of iris mechanisms, or the like, suffer from various disadvantages. When positioned in proximity to a heat-generative, light source, the leaves of the iris elements expand. At areas of overlapping leaves of the iris element, the expansion sometimes results in jamming, i.e., movement of the leaves becomes constrained. And, when movement is constrained, dimming functionality is reduced. Complete blackout of illumination is sometimes not possible as a result of the jamming without the addition of extra leaves or ancillary mechanisms. Additionally, a multi-leaf iris element is relatively complex and also susceptible to damage.
Various other disclosures provide other mechanisms by which to perform light dimming. U.S. Pat. Nos. 1,330,766; 1,460,309; 1,550,600; and 6,769,777 provide disclosure of mechanisms that use controllably-rotatable flaps or luevers. Problems associated with jamming are common, in significant part, and their manufacture is simplified. However, these mechanisms require elements, at all times, to be positioned in the path of the light beam. And, as a result, the full output of a lighting fixture is not possible. While variants of the mechanisms allow flaps or luevers to be withdrawn from the light beam as well as to rotate, such mechanisms are generally prone to jamming and also permits light leakage around the slats or luevers.
U.S. Pat. Nos. 5,590,954; 5,724,625; and 6,241,366 disclose additional mechanical dimmers. These disclosures in general provide mechanisms that use one or more blades that are moved across a light beam to progressively obscure the light output. While these mechanisms are able completely to block light output and to allow all light output of the light source, such mechanisms are generally bulky and extend substantially outside the perimeter of the light beam, resulting in a lighting fixture that is of increased dimensional requirements.
Existing dimming mechanisms suffer from various disadvantages. If an improved dimming mechanism could be provided, improved functionality and performance would be possible.
It is in light of this background information related to light dimmers that the significant improvements of the present invention have evolved.